Relationships Among Physical Activity, Daylight Exposure, and Rest-Activity Circadian Rhythm in Patients With Esophageal and Gastric Cancer: An Exploratory Study

BACKGROUND

Although rest-activity circadian rhythm (RACR) disruption is associated with mortality in patients with cancer, few studies have examined the effect of RACR on patients with esophageal and gastric cancer.

OBJECTIVE

The aim of this study was to identify the predictors of RACR.

METHODS

This cross-sectional, single-site study included 276 patients with esophageal and gastric cancer recruited from chest-surgery and general-surgery outpatient departments. Actigraphy was used to assess objective physical activity (PA), daylight exposure, and RACR, and 3-day PA was used to indicate the subjective amount of PA. The parameter of objective PA was the up activity mean; the parameter of daylight exposure was >500 lx, and the parameters of RACR were the 24-hour correlation coefficient, in-bed less than out-of-bed dichotomy index, midline estimating statistic of rhythm, and amplitude. The subjective amount of PA was calculated as the sum of mild, moderate, and vigorous PA.

RESULTS

The up activity mean predicted 24-hour correlation coefficient. The PA amount and up activity mean predicted in-bed less than out-of-bed dichotomy index. The up activity mean and >500-lx daylight exposure predicted midline estimating statistic of rhythm. Finally, the PA amount and up activity mean predicted the amplitude.

CONCLUSIONS

Increased PA and daylight exposure may improve RACR.

IMPLICATIONS FOR PRACTICE

Patients with esophageal and gastric cancer should be encouraged to engage in outdoor PA during the daytime as part of their regular lifestyle to maintain a robust circadian rhythm.

Effects of odanacatib on bone-turnover markers in osteoporotic postmenopausal women: a post hoc analysis of the LOFT study

This post hoc analysis and modeling study examined the mechanism of action of odanacatib using a statistical model to explain sCTx response in ODN-treated patients as a function of other bone-turnover biomarkers that, with other observed biomarker changes, showed that odanacatib persistently inhibited osteoclastic bone removal activity without preventing osteoclastogenesis.

INTRODUCTION

Odanacatib (ODN) is an oral selective cathepsin K (CatK) inhibitor, previously in development for osteoporosis treatment. A post hoc analysis examined ODN's mechanism of action on bone-turnover biomarkers.

METHODS

A subset of patients who completed 60 months' treatment in the Long-Term Odanacatib Fracture Trial (LOFT; NCT00529373) (N = 112 [57 ODN, 55 placebo]) were evaluated. Serum (s) and urine (u) samples were assayed at baseline and months 6-60 for 10 known bone-remodeling biomarkers: sCTx, uαα- and uββCTx/Cr, uNTx/Cr, sNTx, uDPD/Cr, sICTP, sTRAP5b, sPINP, and sBSAP. Because the CrossLaps® CTx assay identifies the CTx peptide as well as larger molecular weight CTx-containing peptides, including ICTP, a best-fit model was developed to explain the transient sCTx reduction in ODN-treated patients.

RESULTS

ODN persistently reduced the bone-resorption markers sNTx, uNTx/Cr, uαα- and uββCTx/Cr, and uDPD/Cr, and gradually increased the target-engagement marker sICTP and osteoclast number (sTRAP5b), versus placebo from baseline to month 60. sCTx was transiently reduced with ODN within 12 months, returning to baseline by month 48. Modeling suggested that sCTx changes in the ODN group were primarily due to increased accumulation of larger CTx species, including sICTP. The bone-formation markers sPINP and sBSAP showed partial reductions, versus placebo, in the first 6 months but approached baseline by months 48-60.

CONCLUSION

Observed changes in bone-turnover biomarkers support the persistent efficacy of ODN in direct inhibition of osteoclastic bone-resorption activity, without inhibition of osteoclastogenesis. Long-term evaluation also underscores the unique mechanism of ODN on osteoclastic collagen processing and subsequently osteoblastic bone formation.

TRIAL REGISTRATION

NCT00529373.

Predictors of adherence, contamination and dropout in home-based walking by lung and oesophageal cancer patients from two randomised control trials: An exploratory study

OBJECTIVES

In this study, we examined predictors of exercise adherence, contamination and dropout in lung and oesophageal cancer patients who participated in two randomised controlled trials.

METHODS

We used data on 188 lung and oesophageal cancer patients from two previous studies (intervention: moderate-intensity walking for 12 weeks). Baseline measurements included demographic variables, disease characteristics, Hospital Anxiety and Depression Scale and Bouchard 3-day physical activity (PA) record. We used multiple linear and logistic regressions to analyse predictors of exercise adherence in the walking group, contamination in the control group and dropout in both groups.

RESULTS

Pre-intervention exercise habits and baseline depression scores predicted adherence, with an explanatory power of 16.7% (p < 0.0001). Pre-intervention exercise habits (odds ratio [OR] 19.65, 95% confidence interval [CI] 2.76-139.97), baseline moderate PA (min/day) (OR 1.03, 95% CI 1.01-1.05) and baseline vigorous PA (min/day) (OR 1.09, 95% CI 1.01-1.18) predicted contamination. Baseline mild PA (10 min/day) (OR 0.94, 95% CI 0.89-0.99) predicted dropout.

CONCLUSIONS

Pre-intervention exercise habits and baseline depression levels predicted exercise adherence in the walking group. In the control group, pre-intervention exercise habits and baseline moderate and vigorous PA predicted contamination. Baseline mild PA predicted dropout rates in both groups.

Factors affecting mammography screening behaviour among rural Vietnamese women

OBJECTIVES

To identify factors associated with mammography screening behaviour and its predictors among rural Vietnamese women.

METHOD

A predictive correlational study involving 120 women aged ≥ 40 years was conducted in the suburbs of Hanoi, Vietnam, in July 2018 by using Breast Cancer Awareness Measurement and the Champion Health Beliefs Model Scale. Mammography screening behaviour was assessed by asking participants about their previous mammography experience.

RESULTS

Only 16.7% of participants had undergone mammography screening. High education levels, high monthly family income, having family members or friends with breast cancer, and receiving physicians' recommendations increased the likelihood of participants screening for breast cancer. Mean scores on perceived susceptibility and perceived barriers differed significantly between participants who had and those who had not undergone screening (t = 4.31; p < .001; t = -5.05; p < .001, respectively). Perceived susceptibility and perceived barriers significantly increased the predictive power of the hierarchical logistic model (critical value = 6.16; [df = 2]; p = .046). Perceived barriers were the most significant predictors of screening behaviour (odds ratio 0.84; 95% CI, 0.71-0.99; p = .039).

CONCLUSION

Efforts are necessary to increase mammography awareness in the community and promote screening rates in Vietnam.

Primary clear cell sarcoma of the tongue and surgical reconstruction: About a rare case report

Clear cell sarcomas (SCC), also called "soft-tissue melanoma", are rare and aggressive tumors that preferentially affect the lower limbs (tendons and fasciae) and which have also been described in head and neck localizations. Their clinical and immunohistochemical mimicry with melanoma makes it difficult to diagnose sarcomas. SCC treatment is mainly focused on large-scale resection surgery with adjuvant radiotherapy because of their low chemo-sensitivity and extreme lymphophilia. In case of head and neck localization, these treatments may lead to function and aesthetic sequelae thus requiring the use of modern techniques of reconstructive surgery. The authors describe the diagnosis, treatment and follow-up of large lingual SCC case using a DIEP free flap reconstruction according to an original technique developed in the department. Given the characteristics of patients with SCC (a high proportion of women between 20 and 40 years old) and its inherent qualities (low morbidity of the donor site, volume delivered and excellent plasticity), the fascio-cutaneous free flap type "DIEP" "taken according to the design of the" Cathedral triptych seems to be a viable choice among the range of reconstruction solutions.

'I do want to ask, but I can't speak': a qualitative study of ethnic minority women's experiences of communicating with primary health care professionals in remote, rural Vietnam

BACKGROUND

Ethnic minority groups in Vietnam experience economic, social and health inequalities. There are significant disparities in health service utilisation, and cultural, interpersonal and communication barriers impact on quality of care. Eighty per cent of the population of Dien Bien Province belongs to an ethnic minority group, and poor communication between health professionals and ethnic minority women in the maternal health context is a concern for health officials and community leaders. This study explores how ethnic minority women experience communication with primary care health professionals in the maternal and child health setting, with an overall aim to develop strategies to improve health professionals' communication with ethnic minority communities.

METHODS

We used a qualitative focused ethnographic approach and conducted focus group discussions with 37 Thai and Hmong ethnic minority women (currently pregnant or mothers of children under five) in Dien Bien Province. We conducted a thematic analysis.

RESULTS

Ethnic minority women generally reported that health professionals delivered health information in a didactic, one-way style, and there was a reliance on written information (Maternal and Child Health handbook) in place of interpersonal communication. The health information they receive (both verbal and written) was often non-specific, and not context-adjusted for their personal circumstances. Women were therefore required to take a more active role in interpersonal interactions in order to meet their own specific information needs, but they are then faced with other challenges including language and gender differences with health professionals, time constraints, and a reluctance to ask questions. These factors resulted in women interpreting health information in diverse ways, which in turn appeared to impact their health behaviours.

CONCLUSIONS

Fostering two-way communication and patient-centred attitudes among health professionals could help to improve their communication with ethnic minority women. Communication training for health professionals could be included along with the nationwide implementation of written information to improve communication.

Effects of long term treatment with high doses of odanacatib on bone mass, bone strength, and remodeling/modeling in newly ovariectomized monkeys

The objectives here were to evaluate the effects of odanacatib (ODN) at doses exceeding the clinical exposure on biomechanical properties of lumbar vertebrae (LV), hip and central femur (CF), and compare ODN to alendronate (ALN) on bone remodeling/modeling in ovariectomized (OVX) monkeys. Ten days post-surgery, animals were treated with vehicle (VEH), ODN-L (2mg/kg/day, p.o.), ODN-H (8/4mg/kg/day), or ALN (30μg/kg/week, s.c.) for 20months. An intact group was also included. ODN-L provided systemic exposures of 1.8-fold of clinical exposure. ODN-H started at 20-fold for 5.5months, and then reduced to 7.8-fold of clinical exposure, compared to ALN at approximated clinical exposure. From cross sectional analyses, LV density and peak load in ODN at both doses or ALN were not different from VEH or Intact. However, cortical thickness of femoral neck (FN) and CF in ODN were higher (21-34%, p<0.05) than VEH, due to smaller endocortical (Ec) perimeter of FN (10-11%; p<0.05) and CF (9-12%; ODN-L, p<0.05), and larger CF periosteal (Ps) perimeter (2-12%; ODN-H, p<0.001) versus VEH. ODN groups also showed slightly higher cortical porosity and Ps non-lamellar bone in CF. ODN-H treatment resulted in higher CF peak load (p<0.05) versus VEH. For all bone sites analyzed, a positive, linear relationship (r(2)=0.46-0.69, p<0.0001) of peak load to density or structural parameters was demonstrated. No treatment-related differences in the derived intrinsic strength properties were evidenced as compared between groups. ALN reduced all remodeling surfaces without affecting Ps modeling. Trabecular and intracortical remodeling were reduced in ODN groups, similar to ALN. Ec mineralizing surface in ODN-H trended to be lower than VEH by month 20, but Ec bone formation indices in ODN groups generally were not different from VEH. Ps modeling in ODN groups was significantly higher than other treatment groups. This study overall demonstrated the bone safety profile of ODN and its unique mechanism on cortical bone supporting the clinical application for osteoporosis treatment.

Inhibition of bone resorption by the cathepsin K inhibitor odanacatib is fully reversible

The cathepsin K (CatK) inhibitor odanacatib (ODN) is currently being developed for the treatment of osteoporosis. In clinical trials, efficacy and resolution of effect of ODN treatment on bone turnover biomarkers and accrued bone mass have been demonstrated. Here, we examine the effects of continuing treatment and discontinuation of ODN versus alendronate (ALN) on osteoclast (OC) function. First, accessibility and reversible engagement of active CatK in intracellular vesicles and resorption lacunae of actively resorbing OCs were demonstrated by the selective and reversible CatK inhibitors, BODIPY-L-226 (IC50=39nM) and L-873,724 (IC50=0.5nM). Next, mature human OCs on bone slices were treated with vehicle, ODN, or ALN for 2days, followed by either continuing with the same treatment, or replacement of the inhibitors by vehicle for additional times as specified per experimental conditions. Maintaining OCs on ODN or ALN significantly reduced CTx-I release compared to vehicle controls. However, only the treatment of OCs with ODN resulted in the formation of small shallow discrete resorption pits, retention of intracellular vesicles enriched with CatK and other lysosomal enzymes, increase in 1-CTP release and number of TRAP(+) OCs. Upon discontinuation of ODN treatment, OCs rapidly resumed bone resorption activity, as demonstrated by a return of OC functional markers (CTx-I, 1-CTP), cell number and size, morphology and number of resorption pits, and vesicular secretion of CatK toward the respective vehicle levels. As expected, discontinuation of ALN did not reverse the treatment-related inhibition of OC activity in the time frame of the experiment. In summary, this study demonstrated rapid kinetics of inhibition and reversibility of the effects of ODN on OC bone resorption, that differentiated the cellular mechanism of CatK inhibition from that of the bisphosphate antiresorptive ALN.

The effects of the cathepsin K inhibitor odanacatib on osteoclastic bone resorption and vesicular trafficking

Odanacatib (ODN) is a selective, potent and reversible inhibitor of cathepsin K (CatK) that inhibits bone loss in postmenopausal osteoporosis. Evidence from osteoclast (OC) formation from bone marrow of CatK(-/-) mice or human OC progenitors treated with ODN, demonstrated that CatK inhibition has no effect on osteoclastogenesis or survival of OCs. Although having no impact on OC activation, ODN reduces resorption activity as measured by CTx release (IC(50)=9.4 nM) or resorption area (IC(50)=6.5 nM). While untreated cells generate deep trail-like resorption lacunae, treated OCs form small discrete shallow pits. ODN leads to significant accumulation of intracellular vesicles intensely stained for CatK and TRAP. CatK (+) vesicles localize toward the basolateral and functional secretory membranes of the polarized OC and TRAP(+) vesicles evenly distribute in the cytoplasm, suggesting that ODN disrupts multiple vesicular trafficking pathways. Intracellular levels of both precursor and mature TRAP were increased by 2-fold and the pre-pro and mature CatK by 6- and 2-fold in ODN-treated OCs compared to untreated controls. ODN treated OC accumulates labeled degraded bone matrix proteins in CatK containing vesicles. In summary, ODN treatment inhibits bone resorption by blocking degradation of demineralized collagen in the resorption lacunae, and retarding transcytosis for further processing of degraded proteins.

A new osteophyte segmentation algorithm using partial shape model and its applications to rabbit femur anterior cruciate ligament transection via micro-CT imaging

Osteophyte is an additional bony growth on a normal bone surface limiting or stopping motion at a deteriorating joint. Detection and quantification of osteophytes from CT images is helpful in assessing disease status as well as treatment and surgery planning. However, it is difficult to distinguish between osteophytes and healthy bones using simple thresholding or edge/texture features due to the similarity of their material composition. In this paper, we present a new method primarily based active shape model (ASM) to solve this problem and evaluate its application to anterior cruciate ligament transection (ACLT) rabbit femur model via CT imaging. The common idea behind most ASM based segmentation methods is to first build a parametric shape model from a training dataset and apply the model to find a shape instance in a target image. A common challenge with such approaches is that a diseased bone shape is significantly altered at regions with osteophyte deposition misguiding an ASM method and eventually leading to suboptimum segmentations. This difficulty is overcome using a new partial ASM method that uses bone shape over healthy regions and extrapolates it over the diseased region according to the underlying shape model. Finally, osteophytes are segmented by subtracting partial-ASM derived shape from the overall diseased shape. Also, a new semi-automatic method is presented in this paper for efficiently building a 3D shape model for an anatomic region using manual reference of a few anatomically defined fiducial landmarks that are highly reproducible on individuals. Accuracy of the method has been examined on simulated phantoms while reproducibility and sensitivity have been evaluated on CT images of 2-, 4- and 8-week post-ACLT and sham-treated rabbit femurs. Experimental results have shown that the method is highly accurate ( R2 = 0.99), reproducible (ICC = 0.97), and sensitive in detecting disease progression (p-values: 0.065,0.001 and < 0.001 for 2- vs. 4, 4- vs. 8- and 2- vs. 8-weeks, respectively).

Effect of the cathepsin K inhibitor odanacatib on bone resorption biomarkers in healthy postmenopausal women: two double-blind, randomized, placebo-controlled phase I studies

Inhibition of cathepsin K (CatK) is a potential new treatment for osteoporosis. In two double-blind, randomized, placebo-controlled phase I studies, postmenopausal female subjects received odanacatib (ODN), an orally active, potent, and selective CatK inhibitor, once weekly for 3 weeks or once daily for 21 days. Bone turnover biomarkers, safety monitoring, and plasma ODN concentrations were assessed. These studies showed ODN to be well tolerated. Pharmacokinetic (PK) analysis revealed a long half-life (t(1/2); 66-93 h) consistent with once-weekly dosing. Pronounced reductions in C-terminal telopeptide of type I collagen (approximately 62%) and N-terminal telopeptide of type I collagen normalized to creatinine (NTx/Cr) (approximately 62%) at trough (C(168 h)) were seen following weekly administration. Robust reductions in CTx (up to 81%) and NTx/Cr (up to 81%) were seen following daily administration. ODN exhibits robust and sustained suppression of bone resorption biomarkers (CTx and NTx/Cr) at weekly doses > or = 25 mg and daily doses > or = 2.5 mg.

Non-peptide α v β 3 antagonists: Identification of potent, chain-shortened RGD mimetics that incorporate a central pyrrolidinone constraint

Antagonists of the integrin receptor alpha(v)beta(3) are expected to have utility in the treatment of osteoporosis through inhibition of bone resorption. A series of potent, chain-shortened, pyrrolidinone-containing alpha(v)beta(3) receptor antagonists is described. Two sets of diasteromeric pairs of high-affinity antagonists demonstrated marked differences in log P values, which translated into differing dog pharmacokinetic properties. One member of this set was demonstrated to be effective in reducing bone resorption in rats.

Inhibition of osteoclast function by adenovirus expressing antisense protein-tyrosine kinase 2

Osteoclast activation is initiated by adhesion to bone, cytoskeletal rearrangement, formation of the sealing zone, and formation of the polarized ruffled membrane. Previous findings suggest that protein-tyrosine kinase 2 (PYK2), a cytoplasmic kinase related to focal adhesion kinase, participates in these events. This study examines the role of PYK2 in adhesion-mediated signaling and osteoclast function, using PYK2 antisense. We produced a recombinant adenovirus containing a 300-base pair reversed 5'-coding region of PYK2 and used full-length PYK2 as a control. Murine osteoclast-like cells or their mononuclear precursors were generated in a co-culture of bone marrow and osteoblasts. Infection with antisense adenovirus significantly reduced the expression of endogenous PYK2 protein relative to uninfected cells or to cells infected with sense PYK2 and caused: 1) a reduction in osteoclast formation in vitro; 2) inhibition of cell spreading and of actin ring formation in osteoclasts plated on glass or bone and of attachment and spreading of osteoclast precursors plated on vitronectin; 3) inhibition of bone resorption in vitro; 4) marked reduction in p130(Cas) tyrosine phosphorylation; and 5) no change in alpha(v)beta(3) integrin expression or c-Src tyrosine phosphorylation. Taken together, these findings support the hypothesis that PYK2 plays a central role in the adhesion-dependent cytoskeletal organization and sealing zone formation required for osteoclastic bone resorption.

Abnormal localisation and hyperclustering of (alpha)(V)(beta)(3) integrins and associated proteins in Src-deficient or tyrphostin A9-treated osteoclasts

The non-receptor tyrosine kinase Src was shown to be essential for osteoclast function in vivo. We have previously reported that engagement of (alpha)(v)(beta)(3) integrin in osteoclasts induces tyrosine phosphorylation and activation of the adhesion kinase PYK2 and the adaptor protein p130(Cas) in a Src-dependent manner. The objective of this study was to analyse the role of c-Src in the (alpha)(v)(beta)(3) integrin-dependent recruitment of signalling and cytoskeletal molecules in osteoclasts during bone resorption. Using prefusion osteoclasts (pOCs) obtained from cocultures of osteoblasts and spleen cells isolated from Src(-/-) mice or their normal littermates, we found: (1) similar expression levels and ligand binding affinities of (alpha)(v)(beta)(3) integrins in Src(-/-) and Src(+/?) pOCs, (2) reduced adhesion and spreading of Src(-/-) pOCs, (3) defective organisation of the microfilament proteins, F-actin, vinculin and paxillin, and of PYK2 and p130(Cas) in the sealing zone of Src(-/-)OCLs, and (4) hyperclustering of (alpha)(v)(beta)(3) integrins together with microfilament and signalling proteins in the basal membrane of Src-deficient OCLs. In normal OCLs, the tyrosine kinase inhibitor tyrphostin A9 inhibits actin ring formation, bone resorption and tyrosine phosphorylation of several proteins, including c-Src. Furthermore, tyrphostin A9 induced similar hyperclustering of (alpha)(v)(beta)(3) integrins in osteoclasts as observed in Src(-/-) OCLs. Taken together, these findings suggest that normal localisation of (alpha)(v)(beta)(3) and recruitment of its downstream effectors to the appropriate compartments of the osteoclast during resorption depend on Src kinase activity.

PYK2 is an adhesion kinase in macrophages, localized in podosomes and activated by beta(2)-integrin ligation

Pyk2 is a member of the focal adhesion kinase (FAK) family, highly expressed in the central nervous system and haemopoietic cells. Although Pyk2 is homologous to FAK, its role in signaling pathways was shown to be distinct from that of FAK. We show here that Pyk2 is highly expressed in peritoneal IC-21 macrophage and is tyrosine phosphorylated in response to cell attachment to fibronectin and fibrinogen. Upon IC-21 cell adhesion, Pyk2 tyrosine phosphorylation is inhibited by blocking antibodies to the integrin subunits alpha(M) and beta(2). Furthermore, Pyk2 is rapidly tyrosine phosphorylated in response to ligation of beta(2) integrins by antibodies. In migrating macrophages, Pyk2 localizes to perinuclear regions and to podosomes, where it is clustered with tyrosine phosphorylated proteins. Furthermore, in the podosomal ring structure, which surrounds the central actin core, Pyk2 co-localizes with vinculin, talin, and paxillin. In the podosomes, Pyk2 also co-localizes with the integrin alpha(M)beta(2). Lastly, reduction of Pyk2 expression in macrophages leads to inhibition of cell migration. We propose that Pyk2 is functionally linked to the formation of podosomes where it mediates the integrin-cytoskeleton interface and regulates cell spreading and migration.

Nonpeptide alpha(v)beta(3) antagonists. 1. Transformation of a potent, integrin-selective alpha(IIb)beta(3) antagonist into a potent alpha(v)beta(3) antagonist

Modification of the potent fibrinogen receptor (alpha(IIb)beta(3)) antagonist 1 generated compounds with high affinity for the vitronectin receptor alpha(v)beta(3). Sequential modification of the basic N-terminus of 1 led to the identification of the 5,6,7, 8-tetrahydro[1,8]naphthyridine moiety (THN) as a lipophilic, moderately basic N-terminus that provides molecules with excellent potency and selectivity for the integrin receptor alpha(v)beta(3). The THN-containing analogue 5 is a potent inhibitor of bone resorption in vitro and in vivo. In addition, the identification of a novel, nonpeptide radioligand with high affinity to alpha(v)beta(3) is also reported.

Integrins and signaling in osteoclast function

Integrins are heterodimeric adhesion receptors that mediate cell-matrix and cell-cell interactions. Osteoclasts highly express the alphavbeta3 integrin, which binds to a variety of extracellular matrix proteins including vitronectin, osteopontin and bone sialoprotein. RGD-containing peptides, RGD-mimetics and alphavbeta3 blocking antibodies inhibit bone resorption in vitro and in vivo, suggesting that this integrin plays an important role in osteoclast function. RGD-containing peptides were shown to raise cytosolic calcium in osteoclasts. Furthermore, several signaling and adaptor molecules were found to be involved in alphavbeta3 integrin-dependent signaling pathways, including phosphatidylinositol 3-kinase, c-Src, PYK2 and p130(cas). In addition, cytoskeletal molecules such as paxillin, vinculin, gelsolin and F-actin are recruited to adhesion contacts upon integrin activation. Many of these molecules signaling and cytoskeletal localize to the sealing zone of actively resorbing osteoclasts, suggesting that they play a role in linking the adhesion of osteoclasts to the bone matrix with the cytoskeletal organization and the polarization and activation of these cells for bone resorption.

Role of alpha(v)beta(3) integrin in osteoclast migration and formation of the sealing zone

The alpha(v)beta(3) integrin is abundantly expressed in osteoclasts and has been implicated in the regulation of osteoclast function, especially in cell attachment. However, in vivo studies have shown that echistatin, an RGD-containing disintegrin which binds to alpha(v)beta(3), inhibits bone resorption without changing the number of osteoclasts on the bone surface, suggesting inhibition of osteoclast activity. The objective of this study was to examine how occupancy of alpha(v)beta(3) integrins inhibits osteoclast function, using primary rat osteoclasts and murine pre-fusion osteoclast-like cells formed in a co-culture system. We show that: (1) echistatin inhibits bone resorption in vitro at lower concentrations (IC(50)= 0.1 nM) than those required to detach osteoclasts from bone (IC(50) approximately 1 microM); (2) echistatin (IC(50)= 0.1 nM) inhibits M-CSF-induced migration and cell spreading of osteoclasts; (3) alpha(v)beta(3) integrins are localized in podosomes at the leading edge of migrating osteoclasts, whereas, with echistatin treatment (0.1 nM), alpha(v)beta(3) disperses randomly throughout the adhesion surface; and (4) when bone resorption is fully inhibited with echistatin, there is visible disruption of the sealing zone (IC(50)= 13 nM), and alpha(v)beta(3) visualized with confocal microscopy re-distributes from the basolateral membranes to intracellular vesicular structures. Taken together, these findings suggest that alpha(v)beta(3) integrin plays a role in the regulation of two processes required for effective osteoclastic bone resorption: cell migration (IC(50)= 0.1 nM) and maintenance of the sealing zone (IC(50) approximately 10 nM).

Interleukin 1 induces multinucleation and bone-resorbing activity of osteoclasts in the absence of osteoblasts/stromal cells

Interleukin-1 (IL-1) is one of the most potent bone-resorbing factors involved in bone loss associated with inflammation. We previously reported that IL-1 prolonged the survival of multinucleated osteoclast-like cells (OCLs) formed in cocultures of murine osteoblasts/stromal cells and bone marrow cells via the prevention of spontaneously occurring apoptosis. It was reported that macrophage colony-stimulating factor (M-CSF/CSF-1) prolongs the survival of OCLs without the help of osteoblasts/stromal cells. The present study was conducted to determine whether IL-1 also directly induces the multinucleation and activation of OCLs. Mononuclear osteoclast-like cells (prefusion osteoclasts; pOCs) were purified using the "disintegrin" echistatin from cocultures of murine osteoblastic cells (MB 1.8 cells) and bone marrow cells. Both IL-1 and M-CSF prolonged the survival and induced the multinucleation of pOCs through their respective receptors. However, actin ring formation (a functional marker of osteoclasts) by multinucleated cells was observed in the pOC cultures treated with IL-1, but not those treated with M-CSF. We previously reported that enriched multinucleated OCLs as well as pOCs placed on bone/dentine slices formed few resorption pits, but their pit-forming activity was greatly increased by the addition of osteoblasts/stromal cells. Here, pit-forming activity of both pOCs and enriched OCLs placed on dentine slices was induced by adding IL-1, even in the absence of osteoblasts/stromal cells. M-CSF failed to induce pit-forming activity in pOC and enriched OCL cultures. These results indicate that IL-1 induces the multinucleation and bone-resorbing activity of osteoclasts even in the absence of osteoblasts/stromal cells.

Stable association of PYK2 and p130(Cas) in osteoclasts and their co-localization in the sealing zone

Bone resorption is initiated by osteoclast attachment to the mineralized matrix, cytoskeletal reorganization, cellular polarization, and the formation of the sealing zone. The present study examines the interaction between PYK2 and p130(Cas) (Crk-associated substrate), suggested to be part of the signaling pathway initiated by osteoclast adhesion. Using murine osteoclast-like cells (OCLs) and their mononuclear precursors (pOCs), generated in a co-culture of bone marrow and osteoblastic MB1.8 cells, we show that: 1) p130(Cas) is tyrosine-phosphorylated upon adhesion of pOCs to vitronectin or ligation of beta3 integrins; 2) p130(Cas) colocalizes with PYK2 and the cytoskeletal proteins F-actin, vinculin, and paxillin in the podosomal-rich ring-like structures of OCLs plated on glass and in the sealing zone in actively resorbing OCLs on bone; 3) p130(Cas) and PYK2 form a stable complex in pOCs, independent of tyrosine phosphorylation of either molecule, and this complex is present in Src (-/-) OCLs, in which neither protein is phosphorylated or associated with the osteoclast adhesion structure; 4) the association of p130(Cas) and PYK2 is mediated by the SH3 domain of p130(Cas) and the C-terminal domain of PYK2. These findings suggest that p130(Cas) and its association with PYK2 may play an important role in the adhesion-dependent signaling that leads to cytoskeletal reorganization and formation of the sealing zone during osteoclast activation.

Echistatin inhibits the migration of murine prefusion osteoclasts and the formation of multinucleated osteoclast-like cells

The vitronectin receptor alpha(v)beta3 is highly expressed in osteoclasts and was shown to play a critical role in osteoclast function in vivo. The objective of this study was to examine the role of alpha(v)beta3 integrin in osteoclast formation in vitro using the inhibitory disintegrin echistatin, an RGD-containing snake venom. We documented by immunocytochemistry and Northern blot analysis that during murine osteoclast-like cell (OCL) formation in a coculture of mouse osteoblastic MB1.8 cells and bone marrow cells there is increased expression of the alpha(v) and beta3 integrin subunits. Echistatin binds preferentially to the membrane fraction of isolated enriched OCLs (IC50 = 0.6 nM), and this binding is inhibited by vitronectin receptor-blocking polyclonal antibodies. Additionally, cross-linking of radiolabeled echistatin to OCLs, followed by immunoprecipitation with antibodies to vitronectin or fibronectin receptors, shows that alpha(v)beta3 integrin is the predominant receptor for echistatin in this system. In this coculture, echistatin completely inhibits the formation of multinucleated OCLs, but not that of mononuclear prefusion OCLs (pOCs). This inhibition is RGD and dose dependent (IC50 = 0.7 nM). We tested the hypothesis that inhibition of OCL formation may be due to interference with pOC migration and found that echistatin inhibited macrophage colony-stimulating factor-induced migration and fusion of pOCs (IC50 = 1 and 0.6 nM, respectively). Echistatin inhibition of pOCs migration and fusion is also RGD dependent. These results suggest that the integrin alpha(v)beta3 plays a role in pOC migration, which can explain the inhibitory effect of echistatin on multinucleated osteoclast formation in vitro.

PYK2 in osteoclasts is an adhesion kinase, localized in the sealing zone, activated by ligation of alpha(v)beta3 integrin, and phosphorylated by src kinase

Osteoclast activation is initiated by adhesion to the bone surface, followed by cytoskeletal rearrangement, the formation of the sealing zone, and a polarized ruffled membrane. This study shows that PYK2/CAKbeta/RAFTK, a cytoplasmic kinase related to the focal adhesion kinase, is highly expressed in rat osteoclasts in vivo. Using murine osteoclast-like cells (OCLs) or their mononuclear precursors (pOCs), generated in a coculture of bone marrow and osteoblastic MB1.8 cells, we show: (a) tyrosine phosphorylation of PYK2 upon ligation of beta3 integrins or adhesion of pOCs to serum, vitronectin, osteopontin, or fibronectin but not to laminin or collagen; (b) coimmunoprecipitation of PYK2 and c-Src from OCLs; (c) PYK2 binding to the SH2 domains of Src; (d) marked reduction in tyrosine phosphorylation and kinase activity of PYK2 in OCLs derived from Src (-/-) mice, which do not form actin rings and do not resorb bone; (e) PYK2 phosphorylation by exogeneous c-Src; (f) translocation of PYK2 to the Triton X-100 insoluble cytoskeletal fraction upon adhesion; (g) localization of PYK2 in podosomes and the ring-like structures in OCLs plated on glass and in the sealing zone in OCLs plated on bone; and (h) activation of PYK2, in the presence of MB1.8 cells, parallels the formation of sealing zones and pit resorption in vitro and is reduced by echistatin or calcitonin and cytochalasin D. Taken together, these findings suggest that Src-dependent tyrosine phosphorylation of PYK2 is involved in the adhesion-induced formation of the sealing zone, required for osteoclastic bone resorption.

Integrin-mediated signaling in the regulation of osteoclast adhesion and activation

Integrins are heterodimeric membrane receptors that mediate cell-extracellular matrix (ECM), and cell-cell interactions. Integrins provide a physical link between the ECM and the cell cytoskeleton, and transduce signals which lead to elevation of cytosolic pH and calcium levels, changes in phospholipid metabolism and ultimately regulate gene expression. Osteoclast bone resorption is a complicated multistep process, that starts with matrix recognition, osteoclast attachment, polarization and formation of the sealing zone on the bone, followed by the directional secretion of acids and lysosomal enzymes to the resorbing surface. Osteoclasts exhibit high expression of the alpha v beta 3 integrin, which binds to a variety of RGD-containing proteins including vitronectin, osteopontin and bone sialoprotein. RGD-containing peptides, RGD-mimetics and blocking antibodies to alpha v beta 3 integrins were shown to inhibit bone resorption in vitro and in vivo, suggesting that this integrin plays an important role in regulating osteoclast activity. Furthermore, RGD-containing peptides and proteins modulate osteoclastic cytosolic calcium levels. Phosphatidyl inositol 3-kinase and c-Src were co-immunoprecipitated with alpha v beta 3 integrins in these cells. In addition, c-Cbl was found to be a substrate of c-Src in osteoclasts. More recently, ligand-engagement or clustering of alpha v beta 3 integrins in osteoclasts induced tyrosine phosphorylation of PYK2, a member of the focal adhesion kinase family, and of p130cas, a substrate of v-Src and v-Crk. Both PYK2 and p130cas were also found in the sealing zone of actively resorbing osteoclasts. How these signaling molecules interact with each other in mediating the alpha v beta 3 rate limiting effect on bone resorption is not well understood. They emerged however as key players in linking the adhesion of osteoclasts to the bone matrix, to cytoskeletal organization, and to the polarization and activation of these cells for bone resorption.

Tyrosine phosphorylation of p130Cas is involved in actin organization in osteoclasts

Integrin-mediated interaction with the extracellular matrix plays a critical role in the function of osteoclasts, the bone-resorbing cells. This study examines the role of p130Cas (Crk-associated substrate (Cas)) in actin organization in osteoclasts. Multinucleated osteoclast-like cells (OCLs) were obtained in a co-culture of murine bone marrow cells and primary osteoblasts. After plating on culture dishes, OCLs formed a ringlike structure consisting of F-actin dots at cell periphery (actin ring). The percentage of OCLs with actin rings and its diameter increased with time and cell spreading. Tyrosine phosphorylation of a protein (p130) increased with actin ring formation. Treatment with cytochalasin D disrupted actin rings and reduced tyrosine phosphorylation of p130. Using specific antibodies, p130 was identified as Cas. By immunocytochemistry, Cas was localized to the peripheral regions of OCLs and its distribution overlapped that of F-actin. In OCLs derived from Src(-/-) mice, in which osteoclast activity is severely compromised, tyrosine phosphorylation of Cas was markedly reduced. Moreover, Cas was diffusely distributed in the cytoplasm and actin ring formation is not observed. These findings suggest that Src-dependent tyrosine phosphorylation of Cas is involved in the adhesion-induced actin organization associated with osteoclast activation.

The alphavbeta3 integrin regulates alpha5beta1-mediated cell migration toward fibronectin

This study examines the interactions of alphavbeta3 and alpha5beta1 in the regulation of cell migration. Human embryonic kidney (HEK) 293 cells that express alpha5beta1 endogenously were transfected with alphavbeta3 and beta3 mutants, and their attachment and migration to fibronectin (Fn) and vitronectin (Vn) were measured. An alphavbeta3 blocking antibody and the alphavbeta3 ligand cyclic G-Pen-GRGDSPC-A inhibited alpha5beta1-mediated migration toward Fn, but not attachment to Fn. This function was alphavbeta3-specific since alphavbeta5 transfection and alphavbeta5 blocking antibody did not produce this effect. Mutations introduced into the beta3 integrin subunit to dissect this phenomenon revealed the following. Disruption of the ligand binding domain by the Glanzmann thrombasthenia mutation beta3-D119Y constitutively abolished migration toward both Vn and Fn, and attachment to Vn but not to Fn. Insertion of the Glanzmann mutation beta3-S752P into the cytoplasmic domain or its truncation (beta3-Delta717) abolished binding to Vn but not to Fn. Inhibition of migration toward Fn was inhibited in these cells by alphavbeta3 blocking antibody. alphavbeta3-mediated inhibition was, however, abolished by truncation of the transmembrane domain (beta3-Delta693). These findings demonstrate alphavbeta3 regulation of alpha5beta1-mediated cell migration and suggest that the beta3 transmembrane domain is essential for this function.

Arginine-glycine-aspartic acid mimics can identify a transitional activation state of recombinant alphaIIb beta3 in human embryonic kidney 293 cells

The platelet-specific integrin alphaIIb beta3 achieves a high affinity binding state in response to extracellular agonists such as thrombin, ADP, or collagen. During this activation, the receptor undergoes a number of conformational changes. To characterize the different conformations of alphaIIb beta3, we expressed recombinant alphaIIb beta3 in human embryonic kidney (HEK) 293 cells. Antigenic and peptide recognition specificities of the full-length recombinant receptor resembled those of the native receptor in platelets. We used an array of peptidic and nonpeptidic arginine-glycine-aspartic acid (RGD) mimics that specifically bind to human platelet alphaIIb beta3 to determine the affinity state of the receptor. Some of these RGD mimics were previously shown to clearly discriminate between resting and activated alphaIIb beta3. Solution-phase binding of these RGD mimics to the recombinant cells suggested that in HEK 293 cells the full-length alphaIIb beta3 is expressed in a "transitional" activation state. This observation was confirmed by the binding of the activation-specific, monoclonal anti-alphaIIb beta3 antibody PAC1 to cells expressing the full-length recombinant alphaIIb beta3. Deletion of the entire cytoplasmic domain of the beta subunit was sufficient to convert the receptor in HEK 293 cells to a fully active form, as found in activated platelets. In addition, the full-length receptor was capable of mediating agonist-independent aggregation of cells in the presence of fibrinogen. Thus, by using RGD mimics, we have identified a functional transitional activation state of alphaIIb beta3 that is capable of mediating fibrinogen-dependent cell aggregation.

Isolation and characterization of highly enriched, prefusion mouse osteoclastic cells

This study describes the isolation and characterization of highly enriched mammalian osteoclast precursors, released by the "disintegrin" echistatin, from an osteoclast formation culture. Incubation of a 6-day coculture of mouse bone marrow cells and mouse osteoblastic cells (MB1.8) with echistatin (30 nM), an RGD-containing snake venom, for 20 min yielded an 88-95% pure population of tartrate-resistant acid phosphatase-positive cells, 1.5 x 10(5) cells per 150 cm2 culture dish. These cells were mostly mononucleated and based on the following characteristics are considered to be prefusion osteoclasts (pOC cells): (i) presence of calcitonin (CT) receptors documented by 125I-sCT autoradiography and cAMP generation in response to salmon calcitonin; (ii) expression of mRNAs for alpha v beta 3 integrin, osteopontin, 92-kDa type IV collagenase (matrix metalloproteinase 9), carbonic anhydrase II, OC-2 (an "osteoclastic" cysteine proteinase), and protein tyrosine phosphatase epsilon; and (iii) high level expression of pp60c-src protein. The pOC cells resorb bone (form "pits" on bone slices) but only in the presence of osteoblastic MB1.8 cells and 1,25(OH)2D3. Resorption was inhibited by CT. In conclusion, we describe a rapid, reproducible procedure to isolate virtually pure mammalian prefusion osteoclasts, which should help in the study of osteoclast formation, composition, and function.

Synthesis of fully active biotinylated analogues of parathyroid hormone and parathyroid hormone-related protein as tools for the characterization of parathyroid hormone receptors

The synthesis, purification, and characterization of biotinylated analogues of parathyroid hormone (PTH) and PTH-related protein (PTHrP) are described. A novel methodology was developed which allowed the selective biotinylation during solid-phase synthesis of either the Lys13 or Lys26 residue in PTH/PTHrP sequences. Incorporation of orthogonally protected N alpha-Boc-Lys(N epsilon-Fmoc) at a selected position in the sequence, followed by selective side-chain deprotection and biotinylation of the epsilon-amino group, permitted modification of the specific lysine only. Biotinylated analogues of [Nle8,18,Tyr34]bPTH(1-34)NH2 (analogue 1a) were prepared by modification of Lys13 with a biotinyl group (analogue 1) or a biotinyl-epsilon-aminohexanoyl group (analogue 2) or at Lys26 with a biotinyl-epsilon-aminohexanoyl group (analogue 3). A biotinylated PTHrP antagonist [Leu11,D-Trp12,Lys13(N epsilon-(biotinyl-beta-Ala))]PTHrP(7-34)NH2 (analogue 5), was also prepared. In a different synthetic approach, selective modification of the thiol group of [Cys35]PTHrP(1-35)NH2, in solution, with N-biotinyl-N'-(6-maleimidohexanoyl)hydrazide, resulted in analogue 4. The high affinities of the biotinylated analogues for PTH receptors present in human osteosarcoma B-10 cells or in porcine renal cortical membranes (PRCM), were comparable to those of the underivatized parent peptides. The analogues were also highly potent in stimulation of cAMP formation (analogues 1-4) or inhibition of PTH-stimulated adenylyl cyclase (analogue 5) in B-10 cells. The most potent analogue (analogue 1) had potencies in B-10 cells (Kb = 1.5 nM, Km = 0.35 nM) and in porcine renal membranes (Kb = 0.70 nM) identical or similar to those of its parent peptide, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Concentrations of parathyroid hormone-related protein in rat milk change with duration of lactation and interval from previous suckling, but not with milk calcium

PTH-related protein (PTHrP) is found in high concentrations in the milk of various mammals. However, little is known about the regulation of PTHrP production or the physiological role(s) of PTHrP in the mammary glands. To address these questions, we examined in lactating rats 1) the longitudinal changes in PTHrP concentrations in milk and PTHrP mRNA levels in the mammary glands throughout lactation, 2) the effects of the nonsuckling interval on milk PTHrP concentration, and 3) the correlation between PTHrP and calcium concentrations in milk. PTHrP concentrations in milk, measured by RIA and in vitro bioassay, increased with the duration of lactation. The maximal concentrations of PTHrP (observed between days 19-21 of lactation in rats milked serially) were 4.8- to 8.0-fold higher than the concentrations on day 7. PTHrP mRNA levels in the mammary glands also increased during the late stages of lactation. The longitudinal changes in calcium concentrations in milk were small and did not parallel the changes in PTHrP. When pups were removed from the mother for 4-24 h, milk PTHrP decreased while calcium increased in a time-dependent manner. As a whole, calcium concentrations in milk did not correlate with PTHrP throughout lactation. These data suggest that the production and secretion of PTHrP into milk are regulated independently of the other major milk proteins by a factor(s) that changes with progression of lactation and in relation to suckling status.

Suckling-mediated increases in urinary phosphate and 3',5'-cyclic adenosine monophosphate excretion in lactating rats: possible systemic effects of parathyroid hormone-related protein

Earlier studies have shown that lactation-induced bone loss in the rat is both PTH- and vitamin D-independent and have suggested the involvement of another, as yet unidentified, factor(s) in the altered calcium metabolism which accompanies lactation. In the present study, we investigated the possibility that PTH-related protein (PTHrP), which is produced in lactating mammary glands, is a putative calciotropic factor acting systemically during lactation. To test this hypothesis, we examined changes in urinary phosphate and cAMP excretion in relation to suckling since phosphaturia (P-uria) and increased urinary cAMP excretion are sensitive parameters of PTHrP action on the kidney. When lactating rats (separated from their pups overnight) were allowed to suckle pups for 1 h, they showed a marked P-uria which lasted 3-4 h. In most instances, a transient increase in cAMP excretion preceded the P-uria. These effects were not abolished by thyroparathyroidectomy; hence they are not attributable to a transient increase in PTH secretion. Administration of PRL or oxytocin did not induce significant P-uria. When lactating rats were pretreated with anti-PTHrP anti-serum, the suckling-associated P-uria was prolonged and augmented. This prolongation of P-uria was similar to the effects observed when exogenous PTHrP (1-34)amide was administered in the presence of the antiserum. These data support the hypothesis that some of the PTHrP produced in lactating mammary glands may be released systemically during suckling and act in an endocrine manner on target organs such as the kidney.

Expression of the parathyroid hormone-related protein gene in the avian oviduct: potential role as a local modulator of vascular smooth muscle tension and shell gland motility during the egg-laying cycle

The phylogenetic conservation of the primary structure of PTH-related protein (PTHrP) supports an important, yet undetermined, role(s) for this molecule in the biology of birds and mammals. As an initial step toward understanding the function of PTHrP in birds, we investigated the expression of PTHrP mRNA in tissues of the egg-laying hen. This analysis revealed that PTHrP mRNA is expressed at various levels in lung, brain, heart, and tissues of the digestive tract, including the proventriculus (secretory stomach), gizzard, and small intestine. In the oviduct tissues of adult birds, PTHrP mRNA was detected in the isthmus (membrane-secreting) and shell gland (calcium-secreting) portions, but not in magnum (albumin secreting) tissue. During oviduct development, high levels of PTHrP mRNA present in the oviducts of the 12-week-old bird suggest a role for PTHrP in oviduct development. Interestingly, as the oviduct matures, relatively high levels of PTHrP mRNA segregate with the distal tissues that ultimately differentiate into the isthmus and shell gland (uterus). To address a possible role for PTHrP in the differentiated function of the shell gland, we followed the expression of PTHrP in the shell gland at different times in the laying cycle and found levels of PTHrP to transiently increase as the egg moves through the oviduct, gradually returning to basal levels in the 15-h calcification period. We localized the cycle-associated fluctuations in PTHrP mRNA levels to the shell gland serosa and smooth muscle layer. Immunoreactive PTHrP was localized to the serosal membrane as well as the smooth muscle layer of serosal arterioles, suggesting that PTHrP may modulate vascular smooth muscle activity. In support of this hypothesis, synthetic chicken PTHrP (1-34)NH2 was found to relax the resting tension of isolated shell gland blood vessels in a dose-dependent manner. Together, these data indicate that the expression of the PTHrP gene in the avian oviduct is both temporally and spatially regulated during the egg-laying cycle and that PTHrP may function as an autocrine/paracrine modulator of shell gland smooth muscle activity of both ductal and vascular origins. The vasorelaxant property of N-terminal fragments of PTHrP supports a role for this molecule in the temporal increase in blood flow to the shell gland during egg calcification.

The bovine renal parathyroid hormone (PTH) receptor has equal affinity for two different amino acid sequences: the receptor binding domains of PTH and PTH-related protein are located within the 14-34 region

Previous studies examining the interaction of PTH and PTH-related protein (PTHrP) with target tissue have for the most part emphasized the similarity between the two hormones in binding to and activating receptors. This observation that two peptides with limited homology have equal affinities for the same receptor is unusual. In this report we investigated two aspects of PTH/PTHrP-receptor interactions. First, the nonhomologous 14-34 regions of PTH and PTHrP were synthesized and evaluated. Second, hybrid peptides containing the 7-18 fragment of one hormone combined with the 19-34 region of the other hormone were studied to determine whether interactions between these two regions are required for receptor recognition. All four peptides were examined in bovine renal cortical membrane and rat osteosarcoma (ROS 17/2.8) cell PTH-binding and PTH-stimulated adenylate cyclase assays. The results indicate that the receptor-binding domains of PTH and PTHrP lie outside of the 1-13 region, the region containing sequence homology shared by the two hormones, and that two peptides of different amino acid sequence bind with equal affinity to the bovine renal PTH receptor. However, in the absence of the N-terminal region, the rat bone PTH receptor displays a preference for the C-terminal (19-34 sequence) region of PTHrP.

Liquid-chromatographic determination of amiodarone and N-desethylamiodarone in serum

We have developed a stable and simple normal-phase liquid-chromatographic method for simultaneously measuring amiodarone and its metabolite, N-desethylamiodarone, within 8 min. The chromatographic system consists of a 15 cm x 3.9 mm Waters "Resolve" silica column and a mobile phase of ammonium sulfate (17 mmol/L, pH 6.8) and methanol (8/92 by vol), pumped at 1.8 mL/min and monitored at 254 nm. After 250 microL of serum is mixed with 100 microL of 0.36 mol/L NaH2PO4, 100 microL of the internal standard solution (L8040, 6 mg/L), and 200 microL of isopropyl ether, the mixture is vortex-mixed and centrifuged. Fifty microliters of the organic layer is injected onto the column. Relative recovery was 100% over the assay range of 0.1 to 20.0 mg/L for both compounds. Within-run and total (day-to-day) CVs were 3% and 7% for amiodarone and 5% and 8% for N-desethylamiodarone, respectively.

Liquid-chromatographic determination of amiodarone and N-desethylamiodarone in serum

We have developed a stable and simple normal-phase liquid-chromatographic method for simultaneously measuring amiodarone and its metabolite, N-desethylamiodarone, within 8 min. The chromatographic system consists of a 15 cm x 3.9 mm Waters "Resolve" silica column and a mobile phase of ammonium sulfate (17 mmol/L, pH 6.8) and methanol (8/92 by vol), pumped at 1.8 mL/min and monitored at 254 nm. After 250 microL of serum is mixed with 100 microL of 0.36 mol/L NaH2PO4, 100 microL of the internal standard solution (L8040, 6 mg/L), and 200 microL of isopropyl ether, the mixture is vortex-mixed and centrifuged. Fifty microliters of the organic layer is injected onto the column. Relative recovery was 100% over the assay range of 0.1 to 20.0 mg/L for both compounds. Within-run and total (day-to-day) CVs were 3% and 7% for amiodarone and 5% and 8% for N-desethylamiodarone, respectively.

Isolation, characterization, and cDNA cloning of a vampire bat salivary plasminogen activator

Vampire bat saliva contains a plasminogen activator that presumably assists these hematophagous animals during feeding. Here, we report that the vampire bat salivary plasminogen activator, Bat-PA, is homologous to tissue-type plasminogen activator (t-PA) but contains neither a kringle 2 domain nor a plasmin-sensitive processing site. Three Bat-PA species corresponding to full-length, finger-, and finger- epidermal growth factor homology domain- forms of t-PA have been isolated. Bat-PA(H), the full-length form, was purified and its activity has been characterized. Bat-PA(H) and t-PA are of similar efficacy when monitored for their abilities to catalyze plasminogen activation in the presence of a fibrin cofactor. Interestingly, Bat-PA activity toward plasminogen is stimulated 45,000-fold in the presence of fibrin I; the corresponding value for t-PA is only 205-fold. Bat-PA(H) is the only Bat-PA species which binds tightly to fibrin, although each of the three species exhibit remarkable stimulation by a fibrin cofactor.

Purification and characterization of the rat pancreatic cholecystokinin receptor

Cholecystokinin (CCK) is a peptide hormone that has a variety of physiologically important functions in the gastrointestinal tract, in which distinct high affinity receptors have been identified. We describe here the purification of the digitonin-solubilized rat pancreatic receptor as an initial step in the determination of its primary structure. Solubilization of total pancreatic membranes using 1% digitonin resulted in a single class of binding sites with a specific content of 4 pmol/mg as measured in a soluble binding assay using the nonpeptidyl CCK antagonist [3H]3S[-]-N-[2,3-dihydro-1-methyl-2-oxo-5-phenyl-1H-1,4- benzodiazepine-3-yl]-1H-indole-2-carboxamide [( 3H]364,718). The solubilized receptor was purified using the following chromatographic steps: 1) cation exchange; 2) Ulex europaeus agglutinin-I-agarose; and 3) Sephacryl S-300. The final preparation of the purified receptor had a specific content of 8,055 pmol/mg, which represented a 9,051-fold purification from intact membranes. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of the purified receptor preparation under reducing conditions resulted in a predominant polypeptide with an Mr = 85,000-95,000 and minor polypeptides of Mr = 57,000 and 26,000 as determined by radiolabeling and silver staining. Solubilized pancreatic membranes were affinity labeled with the peptidyl CCK agonist 125I-D-Tyr-Gly-[(Nle28,31,6-NO2-Phe33)CCK-26-33] and chromatographed under conditions similar to those described for untreated membranes. Elution of radioactive peaks from each chromatographic column was coincident with [3H]364,718 binding activity and resulted in a labeled polypeptide having the same electrophoretic mobility as receptor derived from freshly labeled membranes and purified from untreated membranes. High performance liquid-gel exclusion chromatography of the crude digitonin-solubilized membrane preparation revealed an estimated molecular size for the [3H]364,718-binding activity of 370,000, which was consistent with the size determined by nondenaturing gel electrophoresis of the purified receptor complexed with the labeled nonpeptidyl antagonist. Binding of [3H]364,718 to the purified receptor preparation was comparable to that observed with the crude solubilized pancreatic membrane preparation; and both the homologous ligand 364,718 (Ki = 0.5 nm) and CCK-8 (Ki = 1.4 microM) competed for binding to both preparations in a similar manner.

Synthetic substrate for eukaryotic signal peptidase. Cleavage of a synthetic peptide analog of the precursor region of preproparathyroid hormone

A synthetic peptide analog of the precursor region of preproparathyroid hormone has been shown to be a specific substrate for hen oviduct signal peptidase. The sequence of the 31-residue peptide is Ser-Ala-Lys-Asp-norleucine (Nle)-Val-Lys-Val-Nle-Ile-Val-Nle-Leu-Ala-Ile-Ala-Phe-Leu-Ala-Arg-Ser-As p-Gly-Lys-Ser-Val-Lys-Lys-Arg-D-Tyr-amide (Caulfield, M. P., Duong, L. T., O'Brien, R., Majzoub, J. A., and Rosenblatt, M. (1988) Mol. Endocrinol. 2, 452-458). This sulfur-free signal peptide analog can be labeled with 125I on the C-terminal D-tyrosine and is cleaved by purified hen oviduct signal peptidase between Gly and Lys, the correct site of cleavage of preproparathyroid hormone in vivo. Amino acid sequence analysis of the cleavage product released 125I at the seventh cycle of Edman degradation, confirming that enzymatic cleavage occurs at the physiological site. Synthetic peptide analogs of the substrate with Lys, Pro, or Asp substituted for Nle-18 were poor substrates for the enzyme and were also poor competitive inhibitors of catalysis, suggesting that modifications at position -18, 12 amino acids from the site of cleavage, directly influence binding by the enzyme. Analysis of the reactivity of signal peptidase with these synthetic peptides provides insight into the cleavage specificity requirements of this eukaryotic signal peptidase.

A chemically synthesized radiolabeled signal peptide: design, preparation, and biological evaluation of an iodinated analog of preproparathyroid hormone

The chemically synthesized signal peptide (native-sequence signal peptide) of preproparathyroid hormone exhibits signal sequence-like activity by inhibiting the translocation/processing of precursor proteins to their mature forms in an in vitro translation system. In order to prepare a biologically functional radiolabeled form of this peptide, we undertook structure-function studies of the native-sequence signal peptide. Since conventional iodination of peptides is performed under oxidizing conditions, chemical design efforts were focused on the oxidation-labile residues, methionine and cysteine, present in the native sequence. Substitution of the three methionines with norleucine and the single cysteine with alanine yielded a surfur-free analog, [Nle-(-25), Nle-(-21),Nle-(-18),Ala-(-14),D-Tyr-(+1)]pre-proPTH-(-29-+1)amide, which is resistant to oxidation and active in the inhibition of processing assay. An interaction between the signal region and one of the components of the intracellular secretory apparatus, signal recognition particle (SRP), was demonstrated: iodinated sulfur-free analog was cross-linked (using the homo-bifunctional reagent disuccinimidyl suberate) to the 54 kilodalton (kDa) subunit of SRP. The 68 kDa and 72 kDa subunits of SRP were also labeled, but to a lesser extent, by the iodinated peptide.

Synthetic signal peptide and analogs display different activities in mammalian and plant in vitro secretion systems

The biological properties of four chemically synthesized signal peptides were compared in mammalian (rabbit reticulocyte) and plant (wheat germ) cell-free protein secretion systems. The precursor-specific region of bovine pre-proparathyroid hormone (preproPTH), [D-Tyr-(+1)]preproPTH-(-29-+1)amide, and a sulfur-free analog, [Nle-(-25), Nle-(-21), Nle-(-18), Ala-(-14), D-Tyr-(+1)]preproPTH-(-29-+1)amide, inhibit the processing of an unrelated precursor protein (pre-prolactin) to its mature secreted form (prolactin) in the mammalian system. In the plant system supplemented with signal recognition particle, the signal peptides arrest translation of both secretory (preprolactin) and cytoplasmic (globin) proteins. One analog, [Nle-(-25), Nle-(-21), Asp-(-18), Ala-(-14), D-Tyr-(+1)]preproPTH-(-29-+1)amide, inhibits preprotein processing in the mammalian system but fails to induce translation arrest in the plant system. A truncated peptide, [N alpha-AcLeu-(-17), Ala-(-14), D-Tyr-(+1)]preproPTH-(-17-+1)amide, lacking the N-terminal (positively charged) region and a portion of the hydrophobic core region, is inactive in both systems. These studies demonstrate that the chemically synthesized signal region of a precursor protein interacts directly with signal recognition particle and functionally mimics the proposed properties of a native signal sequence linked to a nascent protein as it emerges from the ribosome during biosynthesis, and an analog of the signal peptide reveals fundamental differences between the components involved in the protein secretion apparatus in mammals and plants.

Subunit exchange between membranous and soluble forms of bovine dopamine beta-hydroxylase

Dopamine beta-hydroxylase is present in the bovine adrenal medulla in two forms: soluble and membrane-bound. In a previous study, it was shown that the tetrameric, soluble form of the enzyme undergoes dissociation into two identical dimeric subunits and that this subunit dissociation is dependent on pH and ADP binding (Dhawan, S., Hensley, P., Osborne, J. C., Jr., and Fleming, P. J. (1986) J. Biol. Chem. 261, 7680-7684). Here we report the effect of pH and ADP on the dissociation of the membranous form of dopamine beta-hydroxylase into two nonidentical subunits. Negative stain electron microscopy of purified membranous hydroxylase showed largely tetrameric species together with occasional dimeric species. The tetrameric images of membranous hydroxylase were similar to, but clearly different from, previously published negative stain images of soluble hydroxylase (Duong, L. T., Fleming, P. J., and Ornberg, R. L. (1985) J. Biol. Chem. 260, 2393-2398). Quantitative binding of ADP to the membranous hydroxylase revealed the existence of two binding sites per dimeric subunit. ADP binding and low pH both promote dissociation of a hydrophilic, catalytically active subunit from the membranous enzyme reconstituted onto phospholipid vesicles. Kinetic analyses of reconstituted membranous hydroxylase activity were consistent with the existence of tetrameric and dimeric catalytic species in equilibrium. All of the hydrophilic subunits of the purified soluble hydroxylase bind to the hydrophobic subunits of the reconstituted membranous hydroxylase. We propose that, in the chromaffin granules, the soluble hydroxylase subunits are in equilibrium association with the membrane-bound hydroxylase subunits and that the hydrophilic subunits of both soluble and membranous hydroxylase are identical.

Regulation of arginine metabolism in Saccharomyces cerevisiae. Association of arginase and ornithine transcarbamoylase

Association of arginase and ornithine transcarbamoylase (OTCase) has been proposed to play an essential role in the regulation of arginine metabolism in Saccharomyces cerevisiae (Wiame, J.-M. (1971) Curr. Top. Cell. Reg. 4, 1-39). In this report multienzyme complex formation is directly demonstrated in the presence of the active-site ligands for OTCase and arginase. Using equilibrium sedimentation, a dissociation constant for complex formation was determined to be 2.3 X 10(-8) M in the presence of ornithine and agmatine, active-site ligands for OTCase and arginase, respectively. A molecular stoichiometry in the complex of one molecule of OTCase to one molecule of arginase was verified using transmission electron microscopy. The dimensions of the complex were determined by negative staining and rotary and unidirectional shadowing techniques to be 102 A wide by 81 A high. These dimensions are quantitively consistent with dimensions of the individual enzymes (Duong, L. T., Eisenstein, E., Green, S. M., Ornberg, R. L., and Hensley, P. (1986) J. Biol. Chem. 261, 12807-12813). The enzymatic activity of OTCase is virtually completely inhibited when associated with arginase, reflecting the dramatic modulation of enzyme activity as a consequence of the acquisition of quaternary structure in this multienzyme complex.

The quaternary structure of ornithine transcarbamoylase and arginase from Saccharomyces cerevisiae

Electron microscopic studies employing negative staining, rotary shadowing, and unidirectional shadowing have revealed the subunit architecture of ornithine transcarbamoylase and arginase from Saccharomyces cerevisiae. These techniques have confirmed the quaternary structure of these enzymes, and have permitted an estimate of the shape and dimensions of each of the individual enzymes as well as those of the corresponding subunits to be determined. Both enzymes are trimers exhibiting 3-fold rotational symmetry with subunits which are oblate ellipsoids of revolution. The overall dimensions determined for ornithine transcarbamoylase are a height of 39 A and a width of 102 A. The consequent subunit dimensions are 59 X 59 X 39 A, yielding a subunit axial ratio of 1.51. Arginase has a height of 42 A and a width of 97 A. The subunit dimensions are 56 X 56 X 42 A, yielding a subunit axial ratio of 1.33. The hydrodynamic behavior of the two enzymes is fully consistent with this molecular architecture, suggesting that the structures proposed here are similar to those of the proteins in aqueous solution.

Intragranular vesicles: new organelles in the secretory granules of adrenal chromaffin cells

Chromaffin granules from bovine adrenal medullary chromaffin cells have been found to contain small vesicular structures bounded by unit membranes. Detection of these intragranular vesicles within intact cells requires the use of quick-freezing methods. The intragranular vesicles are labile to fixation by aldehydes which explains why they have not been described in intact cells until now. They are found in approximately 60% of the dense-core chromaffin granules in cells and 85% of isolated granules. They are usually clustered in groups of one to as many as five between the core and the inner surface of the granule membrane. The intragranular vesicles are independent vesicles in that they do not appear as simple invaginations of the granule membrane in either serial thin-section or freeze-etch views. Furthermore, they are released from the cell along with granule contents during nicotine-induced secretion of catecholamines. The structural heterogeneity provided by the intragranular vesicles may be related to the functional heterogeneity of granule contents observed in many recent biochemical studies.

Demonstration of post-translational secretion of human placental lactogen by a mammalian in vitro translation system

This study demonstrates the post-translational translocation across the rough endoplasmic reticular membrane of a mammalian secretory protein, human preplacental lactogen. In the rabbit reticulocyte lysate, human preplacental lactogen biosynthesis is arrested by addition of cycloheximide prior to supplementation with dog pancreatic microsomal membranes, which have previously been shown to translocate and process nascent secretory proteins in a cotranslational manner. Twenty-five percent of the precursor protein is consistently converted to its mature form under these post-translational conditions. The resulting mature hormone is resistant to proteolytic degradation by added proteases, thus indicating that it is translocated across the microsomal membrane and sequestered within the lumenal space of the microsomal vesicles. Approximately one-half of the precursor protein synthesized is associated with the ribosomes. Only the ribosome-associated fraction is secreted in this in vitro system, suggesting that the process of post-translational secretion requires ribosomes for protein interaction with the elements of a subcellular secretory apparatus.